Casting easily oxidizable metals



Patented July 19, 1932 UNITED STATES PATENT OFFICE ROBERT J3. WOOD, 01 LAKEWOOD, OHIO, AND FRANCIS G. FRABY, OF OAKMONT, PENN- SYLVANIA, ASSIGNORS, IBY MESNE ASSIGNMENTS, TO MAGNESIUM DEVELOPMENT CORPORATION, A. CORPORATION OF DELAWARE CASTING EASILY OXIDIZABLE METALS No Drawing.

This invention relates to the casting of the easily oxidizable metals, such as magnesium, in sand' molds or molds made of similar agglomerated substances. The invention is particularly directed toward processes and means by which the casting of these metals may be accomplished without the attendant well knowndifliculties heretofore encountered. c

The propensity of the easily oxidizable metals to react violently with moisture and to combine'with oxygen, nitrogen and other gases in the atmosphere has been a serious obstacle to their successful casting in sand molds. In accepted foundry practice there is generally added to the sand or other similar molding materials a tempering medium, usually water, which imparts to the sand the properties necessary to satisfactory molding. Heretofore it has been considered that for successful casting of magnesium filldSilD- ilar metals in such molds, the mold must be carefully heated and the moisture contained therein driven out in order to prevent attack of moisture on the molten metal.

.To overcome these well known diificulties, several methods have been suggested. For example it has been proposed to dry the molds carefully and to incorporate in the 3 molding material a substance which, when the mold becomes heated, will produce a vapor which will surround the metal cast therein and protect it from the atmosphere. Such a protective substances, as they are the property of producing a protecting vapor which in itself has little or no harmful effect on the magnesium or'similar metal.

The principal object of our invention is to provide a protective substance which may be used to advantage in molding mixtures which form the sand molds. into which the, easily oxidiz able metals are cast. The invention has as a further object the production of sound commercial castings of magnesium and similar metals in sand molds.

We have discovered that the compound ammonium phosphate, when incorporated in sand molds and heated by the casting of molten'easily oxidizable metals therein, has

.the surrounding atmosphere.

termed hereinafter, must necessarily have- Application filed October 23, 1929. Serial No. 401,962.

action of the other constituents of the molding mixture aswell as from the action of We have further discovered that this compound exerts'such a protective action in either dried or undried molds.

In the'copending applications of R, T. Wood, filed concurrently herewith, Serial Nos. 410,957, 401,958, 401,959, 401,960, and

401,961, to which reference is made for a more detailed disclosure, there is described a novel process'which in its peferred practice involves the use of a plurality of protective substances, capable of producing metalprotecting vapor at variant temperatures and of collectively producing a more or less contlnuous emission of protective-vapors as the temperature of the mold rises, thus insuring the presence of such vapor in the mold and around the casting, regardless of the temperature to which the mold is brought by the hot metal poured therein. While we have found that ammonium phosphate when employed alone in a molding mixture exerts a very favorable protective effect upon magnesium andits alloys and similar metals, we have also found that ammonium phosphate may be used with advantage as one of a plurality of substances added tothe moldin mixture in accordance with the aforesai method.-

Our experience with various molding sands containing ammonium phosphate smg- 1y or in combination'with other protective substances, has shown that for the production of small size castings the addition of ammonium phosphate a1one, in amounts of l to 3 per cent by weight of the sand produces a mixture having a sufiicient protective action toallow the production of satisfactory castings. In this connection it is not necessary that the mold be dried before use to remove the aqueous tempering medium for we have found that the protective effect produced undera'these circumstances is in most cases adequate even in undried molds.

However, in the production of commercial castings of large size we have found that the aforesaid method of R. T. Wood, in which two or more protective substances are -employed, is productive of thebest results. Consequently when making castings ofan average commercial size or of a large size, we prefer to use with theammonium phosphate one or more other protective substances, as for instance sulfur, ammonium fluorid, naphthalene, glycerin, ethylene and diethylene glycol, and other polyhydric: alcohols, boric acid, ammonium bisulfateyan thracene, potassium sulfid, the compound (w ich we term organic bora formed by' reaction of boric acid and a po yhydric alcohol, borax and a mineral acid, as sulfuric or hydrochloric, urea, ma esium oxalate magnesium fluorid, ammomum chlorid, and ammonium borate.

We prefer, however, to use what we believe to be the best combination comprising our new compound, namely a combinationof a polyhydric alcohol, boric' acid, and ammonium phosphate. The polyhydric alcohol preferably di-ethylene glycol, maybe added 'to the sand in the form of an aqueous solution containing 25 to 75 per cent of the alcohol, and the boric acid may be added in amounts of ,1 to 3 er cent by weight of the total mixture, all 0 which has been described in the copending applications of R. T. Wood aforesaid. The ammonium phosphate under these conditionsis best added in amounts of 1 to 3 per centby weight of the total mixture and usually 2 per cent is found to be ade uate. I V

e have also found that with sand containing only a polyhydric alcohol andammonium phosphate an excellent protective action'on the molten magnesium or similar metal cast therein is obtained. In this instance we ascribethe protective action to the formation of a compound between the poly-- hgdric alcohol and the ammonium phosp ate, which is presumablyan organic phosphate. .The existence of this compound in the heated sand has not been confirmed byus and therefore we suggest it onl as a possible, exgltanation of the beneficial'e ect produced.

her protective substances such as naphthalene,sulfur, ammonium fluorid and other well knownsubstances as Well as ammonium bisulfate and potassium sulfid, the properties of which have been described in the copending applications aforesaid,ma be incorporated with ood results in the molding mixtures described above or one or more of these substances may be added to other molding mixtures, in which ammonium phosphate is present, with beneficial results.

Following are examples of a number of molding mixtures comprising our new compound which may be used with good results m the commercial founding of ma esium and its alloys or other easily oxidizable metals, In these examples andin the appended claims, the term sand is intended Example 1 i A molding mixture consisting of 1 to 3 per cent by weight of ammonium phosphate and sufiici ent water to lend the proper molding properties to the mixture, the balance being san Example .2

A moldin mixture consisting of 2 per cent by weight 'o ammonium phosphate and sulficlent of an aqueous solution of (ii-ethylene glycol containing 25 per cent di-ethylene glycol to lend the proper molding properties to the mixture, the balance being sand.

Example 3 A moldin mixture consisting of 2 per cent by weight 0 cient of an aqueous solution of glycerin containing 50 per cent glycerin. to lend the proper molding properties to the mixture, the balance being sand.

t Example 4 A molding mixture consisting of 2 per cent by weight of ammonium phosphate, 2 per cent, by weight of boric acid, and sufiicient of an aqueous solution containing (ii-ethylene glycol to lend the groper molding properties to the mixture, the 'alance beingsand.

Example 5 l glycol to lend the proper molding properties.

to the mixture, the balance being sand.-

It is'to be understood that the invention is not limited to the forms herein specifically described but can be carried out in other (viva s without departure. from its spirit as We cla1m:

1. The method of casting magnesium and other easily oxidizable metals in sand molds, comprising incorporating in the molding material ammonium phosphate, forming a mold of. {36 mixture, and casting-the metal in the mo 2. he method of castng magnesium and other easily oxidizable metals in sand molds, comprising incorporating in the molding material 2 per cent of ammonium phosphate, forming a mold of the mixture, and casting the metal the mold.

3. Tlfe ethod of casting magnesium and other easily oxidizable metals in sand molds, comprising incorporating in the molding maammonium phosphate and suflied by the following claims. 7 I

ofthe ag-.

terial ammonium phosphate and a polyhydric alcohol, forming a. mold of the mixture, and casting the metal in the mold.

4. The method of casting magnesium and other easily oxidiaable metals in sand molds, comprising incorporating in the molding ma terial ammonium j hos hate and an aqueous solution of a poly ydric alcohol, formin a .mold of the mixture, and casting the metal in the mold.

5. The method of casting magnesium and other easily oxidizable metals in sand molds, comprising incorporating in the'molding material ammonium phosphate and di ethylene is glycol, forming a mold of the mixture, and

casting the metal in the mold. v

6. The method of casting magnesium and other easily oxidizable metals in sand molds, comprising incorporatin in the molding ma- 90 terial ammonium phosp' ate and an aqueous solution containing 25 to 75 per cent of diethylene glycol, "forming a mold of the mix ture, and casting the metal in the mold.

7. The method of casting magnesium and 25 other easily oxidizable metals in sand molds, comprising incorporating in the molding ma terial ammonium phosphate, di-ethylene glycol and boric acid, forming a mold of the mixture, and casting the metal in the mold.

' o 8. The method of casting magnesium and other easily oxidizable metals in sand molds, comprising incorporating in the molding material ammonium phosphate, di-ethylene glycol and 1 to 3 per cent of homo acid, formin 5 a mold of the mixture, and casting the metallinthe mold.

9. The method of casting magnesium and other easily oxidizable metals in said molds, comprising-incorporating in themolding material ammonium hos hate, di-ethy'lene sly- Tool, boricacid an 7 sul ur, forming a mol of the mixture, and casting the metal in the mold.

10. The method of casting magnesium and other easily oxidizable metals, comprising casting "the metal in a mold made of sand containing in admixture therewith a plurality of protective substances of variant vapor- I, izing temperatures, including ammonium .30 phosphate. 1

IL'A mold for casting magnesium and other easily oxidizable metals, made of sand containing ammonium phosphate admixture therewith.

5; In testimony whereof "we hereto aflix our signatures.

' ROBERT T. WOOD. 

